The grass genera of the world
Type species: Lecto: S. schreberi J.F.Gmel.
Including Chauvinia Steud., Limnetis Rich., Ponceletia Thours, Psammophila Schult., Solenachne Steud., Trachynotia Michaux, Tristania Poir.
Habit, vegetative morphology. Perennial; rhizomatous to stoloniferous, or caespitose. Culms 20–300 cm high; herbaceous. Culm nodes glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; tough; broad, or narrow; flat, or rolled; without abaxial multicellular glands; without cross venation; disarticulating from the sheaths; rolled in bud. Ligule present; a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence of spicate main branches (with 2 to many long or short spikes, borne racemosely on the main axis). Inflorescence axes not ending in spikelets (their slender, naked tips often prolonged). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (the rachides dorsiventral, triquetrous); biseriate (appressed or pectinate); sessile.
Female-fertile spikelets. Spikelets 6–18 mm long; abaxial; strongly compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal (the upper longer); exceeding the spikelets; (the upper) long relative to the adjacent lemmas (often exceeding it); free; dorsiventral to the rachis; hairy, or hairless; pointed; shortly awned, or awnless (in Australian representatives); similar (leathery or membranous). Lower glume 1 nerved. Upper glume 1–3 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas not becoming indurated; entire, or incised; when entire pointed, or blunt; not deeply cleft (minutely bidentate); awnless; hairy (shortly), or hairless (glabrous); carinate; 1–3 nerved. Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules absent. Stamens 3. Anthers 3–13 mm long (relatively long); not penicillate. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized; fusiform. Hilum short. Pericarp loosely adherent, or fused. Embryo large. Endosperm hard; without lipid; containing compound starch grains. Embryo with an epiblast, or without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Seedling with a loose coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; erect; many.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous, or lacking. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (walls very thick and pitted), or differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present, or absent; chloridoid-type (sunken in crypts in the epidermis); with partitioning membranes (in S. anglica, S. foliosa). The partitioning membranes in the basal cell. Stomata absent or very rare, or common. Subsidiaries dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs (a few), or not paired (mainly solitary); silicified (usually), or not silicified. Intercostal silica bodies absent, or imperfectly developed; when present, tall-and-narrow, or cubical. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies present throughout the costal zones; horizontally-elongated crenate/sinuous, or horizontally-elongated smooth, or rounded, or tall-and-narrow (or more or less rectangular); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type PCK (S. anglica); XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions present. Maximum number of extension cells 7–10. PCR cells without a suberised lamella. PCR cell chloroplasts with well developed grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (arranged inconspicuously at the bases of the furrows, cf. Ammophila). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Culm anatomy. Culm internode bundles in one or two rings.
Phytochemistry. Tissues of the culm bases with abundant starch. Leaves without flavonoid sulphates (4 species).
Cytology. Chromosome base number, x = 7 and 10. 2n = 28, 40, 42, 60, 62, 84, 120, 122, and 124. 3, 4, 6, 8, and 12 ploid.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Zoysieae; Sporobolinae (as a synonym of Sporobolus). 16 species.
Distribution, phytogeography, ecology. Temperate America, coastal Europe, Africa, Tristan da Cunha.
Commonly adventive. Hydrophytic to helophytic; species of open habitats; halophytic.
Economic aspects. Significant weed species: S. alterniflora, S. cynosuroides. Important native pasture species: S. pectinata.
Rusts and smuts. Rusts Puccinia.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • : S. cynosuröides: P. Beauv. (1812). • S. alterniflora, general aspect: Eng. Bot. (1872). • General aspect (S. maritima): Gibbs Russell et al., 1990. • S. maritima (as S. stricta), general aspect: Eng. Bot. (1872). • Inflorescence branch, detail (S. maritima). • S. maritima, abaxial epidermis of leaf blade: this project. Spartina maritima. Microhairs in crypts (two in lower part of picture, one at top). • S. maritima, TS leaf blade: this project
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 13th November 2017. delta-intkey.com/grass’.